Screw thread grinding machine



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SCREW THREAD GRINDING MACHINE Filed Jan. 8, 1944 1''! Sheets-Sheet l3 July 1, 1947. A. RICKENMANN SCREW THREAD GRINDING MACHINE Filed Jan. 8, 1944 17 Sheets-Sheet 14 'II/IIll/II July 1947- A. RICKENMANN SCREW THREAD GRINDING MACHINE Filed Jan. 8, 1944 17 Sheets-Sheet l5 at E 2 Rs hm on mm m July 1, 1947.

A. RICKENMANN SCREW THREAD GRINDING MACHINE Filed Jan. 8, 1944 17 Sheets-Sheet 16 mam QwN QM gm mi mi QM ZAZSAQS A. RHCKENMANN SCREW THREAD GRINDING MACHINE Filed Jan. 8, 1944 17 Sheets-Sheet 1'7 Patented July 1, 1947 UNITED STATES PATENT OFFICE SCBEW'THREAD GRINDllfIG MACHINE Alfred Rickenmann, Zurich, Switzerland Application January 8, 1944, Serial No. 517,504 In Switzerland April 16, 1942 9 Claims. (CI. 51-95) The present invention relates to thread grindlng machines in which multigrooved grinding disks are used grinding simultaneously a plurality of convolutions of the thread. The invention relates more particularly to thread grinding machines of the said type in which an in- .feed movement of a multl-grooved disc is efwork, the grinding disc operates upon all the convolutions. This manner of grinding which is for instance used for grinding screw threads in shouldered work is known as plunge grinding.

Methods are known to grind threads in cylindrical work pieces by means of a grinding disc having a series of peripheral, annular threadform serrations the length of which disc is less than the length of that portion of the work piece in which threads are to be formed. The work piece is passed axially relatively to the grinding disc the leading end of which is tapering. This method may be called the straight grinding method. If threads are cut by successive operations or strokes, the radial displacement of the grinding disc towards the work piece is adjusted either by hand or automatically. To attain the highest possible efliciency the work to be done by the grinding disc has to be distributed uniformly over the different strokes of the work.

vTherefore if threads are to be cut in several strokes the infeed has to be reduced for-each 'successive stroke so as to grind away successive 2 grinding of the threads is being performed. The grinding disc is advanced towards the work while it passes a flute in the tap.

(2) In grinding screw threads it is not advisable to position the grinding disc in its final radial position-with reference to the'work piece while the latter is at rest and then to grind the convolutions of the threads in but one revolution of the work piece. In doing so the work piece will not be ground truly cylindrical. In the machine-according to the invention the grinding disc is fed to its exact radial working position with reference to the work while the latter is rotating. The grinding of all the convolutions is finished in little more than one full revolution of the work.

(3) With the new machine moreover threads in non-fluted work pieces may be quickly and economically ground with extreme accuracy especially in shouldered work pieces. It is of great importance that in such work the convolutions nearest the shoulder should be of exact profile and diameter and moreover as near as possible to the adjacent flank of the shoulder. Care has to be taken that the feed of the grinding disc is performed at the proper rate with reference to the speed at which the work is rotated. The rate of feeding the grinding disc depends largely on the kind and properties of the material of the work piece. The machine according to this invention allows the feeding at the proper rate found by experience without any aid of an operincrements of the convolutions having the same cross-sectional area. I

An object of the invention is to provide an efiicient machine to perform automatically the said operations by means of a multi-grooved grinding disc the latter being subjected to equal work at each operation or very nearly so.

The machine according to the present invention may be used for grinding taps, ordinary threads, thread cutting hobs and the like, and

may be used also for grinding threads on bolts and for producing and finishing screw threads on'shouldered work.

[The machine may be adapted for instance to perform the following work:

(1) To produce tools as forinstance taps having flutes running transversely to the threads, relieving the teeth of the tap to get a tap of good cutting quality. The relieving is done while the -ator and without having to take recourse to his carefulness. By carefully advancing the grind ingdisc to the depth of the cut, the contours of the grinding disc, the wear of the working faces is greatly minimized and the disc needs less trumg.

The invention consists broadly in a machine for grinding threads comprising means for rotatably supporting the work piece a grinding disc having a plurality of annular grinding serrations or cutting ribs so arranged thereon as to simultaneously work a plurality of threads convolutions of the work piece, means for rotatably supporting said grinding disc, means for producing relative axial movement between the work piece and the grinding disc, and means for automatically producing relative radial movement of work piece and girinding disc so as to grind successive increments in the convolutions of said work piece or to grind the threads at full depth and at about one revolution of the work piece.

Other objects and advantageous details and combinations of parts will appear from the description of the invention shown in the accompanying drawings which illustrate by way of example one embodiment of the new grinding machine and also a modification thereof.

3. In the drawings: Fig. 1 is a side-elevation of the new machine with certain wall portions broken away.

Fig. 2.15 a sectional view on the line 2-2 of Fig. 3 and illustrates the feeding mechanism for the slide of the grinding disc.

Fig. 3 is a side view'of the grinding machine and also illustrates in part ,a section on the line H of Fig. 1.

Fig. 4 is a cross sectional view of the feeding mechanism on the line 4-4 of Fig. 2 in an enlarged scale.

in which the control of the machine is adjusted Fig. 5 is a cross sectional view of the driving elements for the feed mechanism on the; line 6---5 of Fig. 2 in an enlarged scale.

Fig. 6 is a sectional view on the line 6--6 of Fig. 5. k

Fig. '7 is a sectional view of the feeding mechanism for the rolling-in device on the-line 1-1 of Fig. 33.

Fig. 8 is a sectional view on the line 88 of Fig. 1. N

Fig. 9 is a sectional view on the line 9 --9 of of Fig. 1.

Fig. 10 is a sectional view of the; line Ill-l0 of Fig. 9.

Fig. 11 is a sectional view of the line lI-ll of Fig. 9.

Figs. 12, 13 and 14 are sectional views of th damping valve arranged on the slide of the grinding disc substantially on the line l2-l2 of Fig.

2, wherein Fig. 12 illustrates the position of the valve when the slide is in its rearward end position, .while Fig. 13 illustrates the position of the valve during the movement of the slide into; its working position and in the instant the damping device becomes active, and Fig. 14 illustrates the position of the valve during the grinding operation.

' Figs; 15 and 16 illustrate details of the pressure fluid distributor valve in an enlarged scale and in different operative positions. Fig. 15 shows the position of this valve at the beginning of the grinding cycle and Fig. 16 shows the position of the valve atthe end of the grinding cycle. 7 -Fig. 17 is afront view of a feeler which cooperates. with' the feed cams to control the infeed of thegrlnding disc.

Fig. 18 illustrates a group of three cams as it is used during the grinding operation and also indicates the position of the feeler at the beginning ticularly during relief grinding.

Fig. 20 is a cross-sectional view of the distributor valve on the line 20-20 of Fig. 8.

Figs. 21 and 22 illustrate diagrammatically the grinding process. Fig. 21 illustrates the grinding operation during the infeed of the grinding disc while Fig. 22 illustrates the infeed of the grinding tool'when at the same time a relief grinding operation is to be performed, as in grinding the flutes of a tap.

The Figs. 23, 24, 25 and 26 disclose sectional views of a modified feed mechanism, with a simplified control which views correspond to the Figs. 2, 3, 5 and 6 respectively.

Fig. 27 illustrates diagrammatically the control and feed during the grinding of a righthand thread with non-interrupted thread convolutions and automatic infeed of the grinding disc.

Fig. 28 illustrates diagrammatically the control and'feed during the return movement when 'for grinding a-right-hand thread with relief v place automatically. I

Fig. 32 is a top view of the device for rolling in the profiled grooves in the periphery of the grinding disc parts being shown in section on the line li-IB of Fig. 33.

Fig. 33 is a side elevation of the rolling in device and of the means to control the roller with reference to the grinding disc substantially on the line l3"l3 of Fig. 32.

Fig. 34 is a side elevation of the grinding disc and the roller co-operating therewith for profiling the ribs thereof in the line l4i4 of Fig. 32.

Referring to the drawings I is a base upon which is slidably mounted a table 2 on which the work is supported and a tool slide 3 on which the grinding disc S is rotatably mounted on shaft 6. The latterls driven by a motor not shown in the drawing. On the table 2 a head stock 4 is fixedly mounted moreover a tail stock 5 which is adlusta'bly arranged on the table 2. A work spindie I l which is lournalled in the head stock 4, is driven by a motor not shown in the drawing. Said motor drives by a worm I92 and a worm wheel I93 an intermediate shaft l9l (Fig. 1). On a key of shaft l9l a clutch member I9 is slidably mounted. The clutch member l9 may be brought in engagement with either of two spur wheels 20, 2| loosely mounted on shaft IQI. The spur wheel 20 transmits its rotation by two gears 200 and 211i to a shaft! while the spur wheel 2! drives said shaft 9 by a spur wheel 2). By a set of bevel gears I94 a vertical shaft I95 and a worm wheel'drive l0 the shaft 9 drives the work spindle Ii in the one or other direction according to the position of clutch member IS. The table 2 is reclprocated by a lead screw ill. The latter is driven by the shaft 9 by means of atrain of change-speed gears l2 which drive a counter shaft I96 with two gears 410, 412. With the gear 410 a gear 4 is in engagement and with the gears 4H and 412 two toothed rims 414,.413 of a sleeve 41 may be brought in engagement. The sleeve 41 is slidably mounted on a key of the lead screw l 3 and as it may be brought in engagement with either of the gears 410, 411, the direction of the rotation of the lead screw and therefor of the travel of table 2 may be reversed. The sleeve 41 is controlled by a hydraulic piston 48 engaging the sleeve 41 by a fork 415. The piston 46 is controlled by a valve mechanism I8. Both the clutch member l9 and the sleeve 41 may be brought in a neutral position. The valve mechanism l8 comprises a piston 22 which actuates by piston rod 222 and a link 223 a double armed lever 224 the forked lower end of which embraces the sleeve IS. The movements of the piston 22 is controlled by a main controlling valve 23 (Figs.

9 audio). The latter is'rotatably and axially displaceably arranged in a cylinder 36 of the valve body I8. The cylinder 36 is connected by a conduit 48 to a pump P (Fig. 27). A pressure gauge 49 and an automatic relief valve 50 is arranged in said conduit 48. To turn the valve 23 a cap 38| is rotatably mounted in the valve body and on a stud thereof a handle 33 is fastened. A pin 382 of said cap engages a slot 232 allowing the valve piston 23 to slide in axial direction. The handle 38 may be set in any position A, B. C, D indicated in Fig. 1. With the handle 33 in the position A (Figs. 1, 29), the mechanism is set to grind left hand threads the table 2 performing a comparatively long course. If handle 33'is placed into position B (Figs. 1, 27) right hand threads are ground the table 2 performing again along course. When placed in the positionC or D the table 2 travels but a. very small way as usual in the plunge grinding operation, in the one position 0 (Figs. 1, 31) left hand threads are ground and in the position D (Figs. 1, 30) right hand threads are formed.

To control the travel of table 2 the valve 23 and therewith the'piston22 and coupling sleeve l9 have to be operated. To effect this, a pilot piston 233 is arranged in the valve body [8 (figs. .8, 10). In a notch 23| of piston 233 projects the one arm 21 of adouble armed lever 21'-rotatably mounted in the base I. -,The lever 21 is fastened to a shaft 26 on the upper end of which a two armed handle-25 (Figs. 1, 8) is, fastened. One

arm 25| projects'in the path of two dogs 24 adjustablymounted on the table 2. If a dog 24 1 strikes against the arm 25! the shaft 26 is turned and displaces pilot piston 233 by. the arm 21|. The. pilot piston 233 initiates themovement of pist0n=22 by the main valve 23 and piston 22 I shifts the sleeve l9 to connect either of the gears 23, 2| with the driving shaft 9. The reversal of the direction of rotation of shaft 9 occasions a reversal in the direction of rotation of shaft II and lead screw l3 and of the travel of table 2.

In plunge grinding the table 2 has to travel but a very short wayand the work spindle performs but very few rotations. The reversing mounted on a shaft 33 (Fig. 8) rotatably mounted in the base The hub of the worm wheel 32 forms a piston sliding in a bore 322 of valve body |8 (Fig. 9) to which oil under pressure can pass by a channel. controlled by valve 23. The worm wheel 32 is provided on its outer face with teeth which by axial displacement of worm wheel 32 may be brought in engagement with a clutch member 31 rigidly fixed to shaft 33. The worm wheel 32 is kept out of engagement by a spring 45 arranged in a bore 330 of the shaft 33. One end of the spring is attached to a pin 33| near the end of the bore and the other end to a pin 332 crossing the bore 45 and passing through slots 33 the ends being attached to a ring 32| slidably on the shaft 33 and arranged in a recess of worm wheel 32. By passing oil under pressure from channel 4| into the bore 322 the worm wheel 32 is displaced in axial direction on the shaft 33 against the action of spring 45. When worm wheel 32 is in mesh with the clutch member 31 the rotations of worm wheel 32 and therewith 6 of shaft 9 are transmitted to shaft 33. On the latter a cam disk 28 (Figs. 8, 20) is fixed, and adjacent thereto a cam disk 29 fastened on a sleeve 42 rotatably mounted in the base The opposite faces 28|, 29| are apart by an angle a. In this gap projects one arm 212 of lever 21. By turning shaft 33 the faces 28|,' 29| strike alternatively against arm 212 turning the lever 21 which by its arm 21| shifts the pilot piston 233. The cam discs 28 and 29, which are independent of the dogs 24, are adjustable relatively to each other. For the purpose of changing the angle a: the sleeve 42 on which the cam disc 29 is fixed, is

rotated relative to the shaft 33. The sleeve 42 is provided with a conical recess 42| into which projects a cone 432 connected to shaft 33 by a key I. By a-nut 44 the cone 432 may be pressed into the recess 42| and then sleeve 42 and disk 29 take part on the rotation of shaft 33. Loosening of thenut 44 permits a rotative adjustment of the sleeve 42 relative to the shaft 33. The work spindle II and the shaft 33 are both driven by shaft 9 at a certain predetermined ratio. The sleeve 42 is provided with markings and the cone 43 with an index. The division lines are numbered the number opopsite of the index gives the size of angle a and therewith the number of turns which the work spindle II has to perform until a reversing takes place.

The cylinder of the pilot valve 233 communicates with the cylinder of the main controlling valve 23 by conduits 234, 235 and 236 (Figs. 2'1 to 31). 011 under pressure passes from cylinder 231 of the valve 23 to pilot valve 233 by the conduit 234. In the position of the piston of pilot valve 233 at the left end of its stroke (Figs. 24, 27 to 31) oil passes through conduit 235 into the cylinder 231 and shifts the piston 23 on to'the face 38 (Fig. 9) of the cap 38L The oil passes on through conduit 35 into cylinder 36 and pushes the piston 22 to the right (Figs. 10, 11). The piston 22 shifts the sleeve l9 to the left (Fig. 1), by means of piston rod 222, link 223 and lever 224. The table 2 and the work spindle perform now their working stroke. To initiate the return stroke of table 2 and spindle H the lever 21 has to be re-set to shift the piston of the pilot valve 233 to the right (Figs. 10, 27 to 31). In this position oil under pressure passes through conduit 236 into the cylinder 238 of the main valve 23 while the cylinder 231 is emptied, the oil flowing off by the conduits 235, 239. The piston of valve 23 moves until it comes to rest on the face |8l. Oil under pressure passes now through conduit 34 into the cylinder 3 and shifts the piston 22 to the left (Fig. 10), oil flows off from cylinder 36 through conduit 35 and channels in the valve 23 into the flow-off pipe 23| l. The piston 22 moving to the left (Fig. 10)

moves the sleeve |9 again in engagement with the wheel 20. The table 2 returns to its initial position and the spindle turns backwardly. A new cycle of operation may now start as described.

If right hand threads are to be ground the table 2 is moved from the left to the right (Fig. 1) during the working stroke and in opposite direction when left hand threads are to be ground. In grinding left hand threads the piston of the pilot valve 233 has to initiate a working stroke when it is moved to the right (Fig. 10). In this case the piston of valve 23 is moved until it comes to rest on the face |8| (Fig. 27). The hand lever 38 is in its position A. In the conduit 35 is now oil under pressure, the piston 22 is moved to the right (Fig. 10) and the sleeve Hi to the left (Fig. 1) engaging thereby the wheel 2|. 

